This invention relates to a machine tool with a turret for receiving tools, with a drum magazine for storing further tools and with an automatic device for conveying the tools from the magazine into a working position on the turret.
Machine tools of this type are generally known. As an example of the prior art, reference is made to German Offenlegungsschrift No. 1,477,429 which discloses a milling machine in which the magazine is arranged above the drum turret. Therefore, a relatively complicated and costly mechanism is required for conveying tools from the magazine to the drum turret in the working position. In addition, considerable time is required for transporting a tool from the magazine to the turret, during which time the machine tool must be stationary, thereby increasing the idle times of the latter. In the construction known from the above publication there is no danger of a collision between unused tools and the workpiece or with the clamping mechanism, because in the drum magazine the tools are stored at a right angle to the axis of the tools in the drum turret.
In order to reduce idle times and simplify constructional expenditure compared with constructions having intermediate magazines, lathes have been constructed with two turrets of different diameters positioned coaxially with respect to one another. German Offenlegungsschrift No. 2,656,608 shows such a construction, wherein the inner turret carries the tools for machining external diameters, whilst the outer turret carries tools for machining the internal diameters. To make it possible to use the tools of the inner turret, a sector is cut out of the outer turret, but the freedom from collisions is not satisfactory because, when machining external diameters, there is a danger that tools for machining the internal diameters will radially collide with the chuck of the work spindle or the workpiece to be machined. The smaller the sector in the outer turret which is not occupied by tools, the greater said risk. However, if for avoiding collision problems said sector is made as large as possible, the number of tools which can be arranged on the outer turret is reduced, which is economically undesirable. In addition, the tools on the outer turret must have such a reciprocal spacing that they do not mutually impede one another during the machining of internal diameters. When machining internal diameters, there is a risk of the tools for machining the external diameters axially colliding with the chuck of the work spindle or with the workpiece to be machined. To reduce this risk, the two turrets disclosed in German Offenlegungsschrift No. 2,656,608 are at an angle to one another but this significantly increases the cost of turret construction.